The 26-year-old, who appears to become increasingly radicalized over the last few years, was killed in a shoot-out with police on Thursday night.

Friends revealed that Tamerlan was changed by the murder of best friend Brendan Mess.

Two years ago Mess and two other men - Raphael Teken and Erik Weissman - were murdered on September 12, 2011.

Their bodies were found covered in marijuana in an apartment in Waltham, Massachusetts, and had their throats slit with a knife or ice pick.

Initially police said two other people had been there on the day and they were looking to question them although no one has ever been charged.

Wai Kru Mixed Martial Arts center owner John Allan said Tsarnaev and Mess used to work out at his gym together but Tsarnaev stopped coming after Mess was murdered.

The event clearly still haunted Tsarnaev as recently as last week when he suddenly returned to his old gym and started acting unusually.

The business owner who was traveling in Thailand at the time said he received an e-mail saying Tsarnaev had been in but acted rudely and disrespectfully to other gym-users.

'It was a clear indication that something was up,' Allan told the Boston Globe. 'He was becoming a complete [expletive].'

Dark past: Tamerlan, pictured in the gym in 2009, was arrested that year on suspicion of assaulting his girlfriend (not pictured)

Tamerlan was an avid boxer and spent a lot of time training for competitions, according to Johannes Hirn, who posted a photo essay entitled 'Will Box for Passport'

Family members reported that Tamerlan seemed to become more devout from 2009.

Aunt Maret Tsarnaeva said her nephew went from praying no more than once a day to praying five times a day.

A neighbor reported he started changing his dress while his uncle said he lectured him on religion in 2009.

'There certainly were mentors,’ Ruslan Tsarni
said. 'I was shocked when I heard his words, his phrases, when every
other word he starts sticking in words of God.

'I question what he’s
doing for work, (and) he claimed he would just put everything in the
will of God. It was a big concern to me. He called me 'confused' when I
started explaining to him, make yourself useful to yourself and to your
family and maybe you’ll have extra to share with everybody else.

'It wasn’t devotion, it was something,
as it’s called, being radicalized. Not understanding what he is talking
(about). He is just using words for the sake of the words and not
understanding the meaning of it.’

It was in recent months however that
he appeared to become radicalized, posting about terrorism online from
around five months ago.

'I used to warn Dzhokhar that
Tamerlan was up to no good,' Zaur Tsarnaev, 26, the suspects cousin from
Makhachkala, Russia, said.

'[Tamerlan] was always getting in
trouble. He was never happy, never cheering, never smiling. He used to
strike his girlfriend. . . . He was not a nice man.'

'He could manipulate him,' an uncle told the New York Times.

They painted a picture of Dzhokhar as the weaker of the pair led astray by his older sibling.

Peter Tean, 21, a high school wrestling teammate, said that he thought Dzhokhar copied his brother's love of boxing by taking up the sport.

'He’s done these violent sports because his brother’s a boxer,' Mr. Tean told the Boston Globe. 'He really loves his brother, looks up to him.'

Convert: A woman believed to be Katherine Russell, the wife of Boston bomber Tamerlan Tsarnaev outside her family's Rhode Island home today

Middle class family: Katherine Russell's mother Judith, above, on the left, is a nurse, while her sister Anna, is at college

He was described as settled in America with a good network of friends.

The family appears to have been torn apart with Tsarnaev falling out with his uncleAlvi Tsarnaev two years ago.

He phoned him the night before he was
killed asking for 'forgiveness'. The uncle from Montgomery Village,
Maryland, didn't reveal what the disagreement was about.

'He said, 'I love you and forgive me,' he said

'We
were not talking for a long time because there were some problems. We were not happy with each other.'

'I asked him what he was doing. He said, "I fix cars, I got married, got a baby,'

'Killing innocent people, I cannot forgive that,' he said. 'It's crazy. I don't believe it now even. How can I forgive this?'

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Tsarnaev also had a child, 3-year-old Zahara, with a 24-year-old college graduate, Katherine Russell, who converted to Islam.

The 26-year-old man was regularly seen at the 24-year-old woman’s family
home in Rhode Island but it appears they had separated.

Yesterday her family’s home was being raided by the FBI.

One neighbor told MailOnline how the brunette converted to Islam shortly after
starting college.

Speaking from the quiet suburb, the neighbor said: ‘She went away to college about three or four years ago and I saw her a
year later and she was dressed in the Islamic style. Her hair was
covered and she was wearing very baggy, flowy clothing.’

However, the neighbor said the last time she saw her husband was a year ago, adding: ‘She moved back home
and was living at home with the baby.

‘I never saw him again, I thought maybe he’s gone away or he’s busy with school.’

The relationship was clearly troubled early on with Tamerlan being arrested for domestic violence in 2009.

Band of brothers: Tamerlan Tsarnaev, fifth from left, top row, poses with his team at 2010 New England Golden Gloves Championship in Lowell, Mass.

It was recently that it appeared his thoughts may have turned to terrorism.

He had a channel on YouTube opened in August 2012 and five months ago created a playlist dedicated to terrorism.

Named simply ‘Terrorists,’ the playlist included a pair of videos, which are now no longer available.

Although most of the clips in the channel are ordinary music videos, Tamerlan Tsarnaev’s YouTube channel shows signs that he had been drawn to radical Islamism.

Among the songs on his playlists was one called ‘I will dedicate my life to Jihad.' He also featured videos recorded by recent converts to Islam.

The 26-year-old former boxer also appeared to favor radical sermons by an Australian Muslim preacher of Lebanese descent best known for calling for the beheading of a right-wing Dutch politician.

Feiz Mohammad, who like Tamerlan was also a boxer, has gained notoriety for preaching an extreme form of Sunni Islam closely associated with al-Qaeda known as Salafism, The Daily Beast reported.

In 2007, the sheik came under fire for calling on young Muslims to become Jihadis.

Tsarnaev also allegedly fell under the influence of Abdel al-Hamid al-Juhani, who has been accused of working to expand the influence of al-Qaeda in Chechnya and the Caucasus.

Man of many talents: Besides boxing, Tamerlan (right) studied accounting, wanted to become an engineer and played the piano and violin

National identity: Tamerlan said in an article that unless Chechnya becomes independent, he would rather compete for the US than for Russia

American dream: Representing New England in 2010 National Golden Gloves competition in Utah, Tsarnaev said he wanted to be 'selected for the US Olympic team and be [a] naturalized American'

NBC 4 New Yorkreported
Friday that Tamerlan Tsarnaev flew in and out of John F. Kennedy
Airport last year and spent six months out of the country, raising the
possibility that he may have received terror training abroad.

Travel
records obtained by the station show that the 26-year-old left New York
January 12, 2012, en route to Moscow. He returned to JFK July 17.

Documents
show a photo of a bearded Tsarnaev. According to the records, he was
born October 21, 1986 and first entered US through JFK July 19, 2003.

Tamerlan Tsarnaev was an avid boxer
and spent a lot of time training for competitions, according to
Johannes Hirn, who posted a photo essay entitled ‘Will Box for Passport’
on his page on Photoshelter.com.

Representing
New England in 2010 National Golden Gloves competition in Utah,
Tamerlan Tsarnaev dreamed of being ‘selected for the US Olympic team and
be [a] naturalized American.’

‘Unless his native Chechnya becomes
independent, Tamerlan says he would rather compete for the United States
than for Russia,’ reads the caption to one of the pictures that shows
Tamerlan during his workout.

In fighting form: Tamerlan Tsamaev (R) and Lamar Fenner (L) stand during a decision in the 201-pound division boxing match during the 2009 Golden Gloves National Tournament of Champions May 4, 2009 in Salt Lake City, Utah

Quiet guy: Tamerlan's (left) former coach described him as a subdued, nice young man who kept to himself

Brute force: One former team member said that Tsarnaev was aggressive in bouts but showed little skill

Loner: Those who knew the 26-year-old from his boxing days said he would never spend time with his team members and at times had a bad attitude

The photo essay also reveals that Tsarnaev had a half-Italian, half-Portuguese girlfriend who had converted to Islam, that he drove a Mercedes and loved the movie 'Borat.'

Tamerlan,
who was affiliated with a Team Lowell club, won the Rocky Marciano
Trophy as New England Golden Gloves heavyweight champion in 2010.

Tsarnaev boxed in a 2004 tournament as part of the Golden Gloves tournament, telling The Lowell Sun newspaper at the time, 'I like the USA.'

He said that his first love was music, and that he played the piano and violin.

According to TMZ, Tamerlan was a major hip-hop enthusiast and even belonged to a fan website called Real-hiphop.com.

Messages posted on Dzhokhar Tsarnaev's Twitter account reveal that he too liked that genre of music, even quoting lyrics by Jay-Z.

Islamist: Five months ago, Tamerlan created a playlist on his YouTube page dedicated to terrorism

Named simply 'Terrorists,' the playlist included a pair of videos, which are now no longer available

Troubling: Although most of the clips in the channel are ordinary music videos, among the songs was one called 'I will dedicate my life to Jihad'

Tamerlan studied accounting as a part-time student at Bunker Hill Community College in Boston.

School officials say that the 26-year-old attended classes there for three semesters: fall 2006, spring 2007 and fall 2008.

According to a profile that appeared in a Boston University magazine in 2010, Tamerlan wanted to become an engineer.

Spokeswoman Patricia Brady said Friday they had little information on Tsarnaev other than that he studied accounting at the Boston school.

Family members said he was unemployed.

The Tsarnaev family, which also
includes two daughters, Bella and Amina, had the status of refugees at
the time they moved to Makhachkala, the capital of Dagistan, from the war-torn Kyrgyzstan in the 1990s.

The parents and Dzhokhar Tsarnaev emigrated to the US first in 2002. Tamerlan Tsarnaev and his sisters lived for a few months with relatives in Kazakhstan before reuniting with their parents in 2003, according to his aunt.

Despite
spending much of his life in the US and being involved in sports,
the English-language channel RT America reports that he claimed to have but 'a single American friend.'

Fighter: Counterterrorism officials believe Tamerlan and his brother had some military training

Tamerlan Tsarnaev (right) became a permanent US resident in 2007, about four years after seeking asylum in the US

Traditional values: While appearing like an all-American 20-something man, Tamerlan said in an interview that he is a devout Muslim who does not drink and upholds traditional values

New twist: Tsarnaev flew in and out of John F. Kennedy Airport last year and was out of the country for six months

'I don't understand them [Americans],' reads a caption below a set of pictures showing Tamerlan obtained by the news site.

Tamerlan's former boxing coach John Curran told the Boston
Herald that in the two years he had spent training the boxer, he never noticed
any radical tendencies in the fighter

'In the gym I never saw any hatred or nothing like that,'
Curran said. 'He would walk in, shake hands, say hello, do his work, shake my
hand and say good night. Every night. I’m shocked.'

Conspiracy theory: The siblings' mother, Zubeidat Tsarnaeva, said in an interview that her sons are '100 per cent innocent,' and that they have been framed

Curran recalled how Tamerlan, whom he described as a 'talented
kid,'would bring his younger brother to
the gym to exercise, adding that the 19-year-old 'idolized' his sibling.

The coach said that although he knew Tamerlan was Muslim,
the boxer hardly ever spoke of his faith.

'The only Muslim comment he ever made to me was that he was
going to marry a good Muslim girl,' Curran said.

Former Golden Gloves competitor Tommy Duquette, who knew the
older Tsarnaev brother slightly, described him as unskilled but aggressive.

Duquette also said that the 26-year-old man was 'a loner,
kind of weird,' usually opting to stay in his room rather than spend time
with his teammates.

Russell Lamour, who fought on the 2009 national team, sounded a similar
note, telling Herald that Tamerlan mostly kept to himself.

'When I first realized it was him, I was really shocked. I
didn’t think he’d be one to want to hurt people like that.

'But he did have an attitude around guys, like "Don’t
mess with me." Like, if people joked with him and he didn’t understand it
was a joke, he’d get angry and upset.'

The
elder Tsaranaev, described by his uncle Ruslan Tsarni Friday as a 'loser,' was
arrested in 2009 for allegedly assaulting his girlfriend, according to the City of
Cambridge Police Department.

Aunt speaks: Maret Tsarnaeva, an aunt of the two suspects in the Boston Marathon bombing, holds a reporter's smart phone which displays a scene from the bomb site, as she speaks to journalists in the lobby of her apartment building in Toronto

VIDEO 'Show me the evidence.' Maret Tsarnaev defends brothers

The family's second run-in with the
law came in June 2012, when the boys' mother, Zubeidat Tsarnaeva, was
arrested for stealing $1,624 in clothes from the high-end store Lord and Taylor.

In the aftermath of his older son’s
death during a gunfight with police, the father of the suspects said
that his slain son was a devout Muslim.

‘Tamerlan says he doesn't drink or
smoke anymore: 'God said no alcohol.' A Muslim, he says: 'There are no
values anymore,' and worries that 'people can't control themselves,’
Anzor Tsarnaev told the The Associated Press by telephone from the
Russian city of Makhachkala.

The suspected bombers parents separated and Anzor's sister said he moved back to Russia after being attacked in Boston and beaten up.

Maret, a lawyer, said the brothers'
father spent several years in America but left after being beaten on the
streets of Boston. She did not go into any details of the attack.

She also claimed her father -- the
suspected bombers' grandfather -- had been 'blown to bits' in an
unexplained incident in Russia.

Tamerlan was caught on surveillance footage moments after the Boston marathon bombing. He walked ahead by about 10
feet.

He was
stockier, in khaki pants, a light T-shirt, and a dark jacket. The brim
of his baseball cap faced forward, and he may have been wearing
sunglasses.

Final farewell: An uncle, Alvi Tsarnaev, got a call from Tamerlan just hours before he was shot dead, with the nephew telling his relative that he had a baby

Harsh words: Ruslan Tsarni, the uncle of the Boston Marathon bombing suspect, called his nephews 'losers' and said that they brought shame on their family before urging Dzhokhar to turn himself in

'Role model': Among the videos posted on his channel were sermons by Australian preacher Feiz Mohammad, who has gained notoriety for calling for the beheading of a right-wing Dutch politician

Children play in front of School No. 1 in Makhachkala, the capital of Dagestan, a predominantly Muslim republic in southern Russia, where Dzhokhar Tsarnaev allegedly went to school

Wanted: This combination of photos provided by the FBI, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev.

Carnage: Three people were killed and over 170 were injured when two bombs exploded on 15 April 2013 at the finish line of the Boston Marathon